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Finding the Words: New Brain Stimulation Technique Shows Promise for People with Aphasia

October 6, 2010

A stroke, the medical term for when blood and nutrients are cut off from the brain, can have a devastating effect on a person’s ability to communicate. Words that once came naturally for even simple objects before the stroke—such as a chair, a pen, or an apple—are suddenly difficult if not impossible to retrieve. Although some people may recover their language skills in time, for others, the effects can be chronically debilitating.

Such differences in patient outcomes have scientists from the University of South Carolina delving deeper into this language disorder—called aphasia—which results when language centers of the brain are damaged by stroke, head injury, or other causes. In new NIDCD-funded research, they’ve demonstrated not only how important the location of the brain damage is in predicting how well a person will respond to aphasia therapy, they are also investigating a new method for stimulating brain-damaged regions in people with aphasia, in hopes of increasing brain plasticity and perhaps improving word recall.

In research published in the September 15, 2010, issue of the Journal of Neuroscience, Julius Fridriksson, Ph.D., studied 26 patients who experienced chronic aphasia after suffering a stroke that damaged the brain’s left hemisphere, where the language centers are found. He wanted to observe whether treating patients for anomia, an impairment associated with aphasia in which a person has difficulty naming certain objects, can help increase neural activity in key regions of the brain. (Although there are several types of aphasia and each has a variety of symptoms, anomia is a symptom that all people with aphasia have in common.) He also wanted to learn if damage to certain regions of the brain had a particularly negative effect on the successfulness of a patient’s treatment.

At the start of the study, brain scans were taken using structural magnetic resonance imaging (MRI) to help pinpoint the location of each participant’s brain lesions. Functional MRI was then used to record any changes in brain activity before, during, and after two weeks of standard anomia treatment. During the treatment phase, two types of cues —phonological or semantic—were given for one week at a time to participants to help them remember the names of pictured objects. For example, for the phonological treatment, the researcher might show a picture of a pen and say “It starts with puh” or “It rhymes with hen.” A cue during the semantic treatment might be, “It’s something that you use to write with.” If after several cues a participant still could not name the object, he or she was given the word and asked to repeat it over and over.

Upon completion of the procedure, Dr. Fridriksson noticed that some participants showed great improvement in their ability to name objects while others showed little change. Participants whose lesions were located in areas specializing in word retrieval and phonological processing, toward the back of the left hemisphere, experienced significantly poorer results than participants whose lesions were located elsewhere. He also found that improvement in naming ability was closely tied to brain activation in regions toward the front as well as farther back in the brain’s left hemisphere.

“In the past, people have always wondered how the brain mediates recovery. Is it the whole brain, is it the right hemisphere that picks up the slack, or is it the rest of the damaged left hemisphere that changes to promote recovery?” said Dr. Fridriksson. “And what this study clearly shows is for those patients who do well in treatment, the damaged hemisphere changes and supports that recovery.”

With this in mind, Dr. Fridriksson and his team wondered if they could do anything to further spark these damaged yet functioning brain regions into action.

In a paper that appeared in the June 2010 issue of Stroke, Julie Baker, Ph.D., who was working on her dissertation under Dr. Fridriksson, used transcranial direct-current stimulation (tDCS)—a low-current stimulation technique that is safe, non-invasive, and barely detectable to the wearer —to attempt to further stimulate areas of the brain that are already activated during word retrieval. Studying 10 patients with aphasia, Dr. Baker compared tDCS to a placebo technique while participants were engaged in a computer program to improve their ability to name objects. For five consecutive days, 20 minutes per day, participants would receive either the real tDCS or the placebo as they took part in the computerized treatment. After a one-week break, they resumed with 5 more days of treatment and the other stimulation technique, real or placebo. Dr. Baker then compared the number of words participants could name before and after treatment.

Dr. Baker found that, for all of the patients enrolled in the study, the numbers of correctly identified names following tDCS stimulation were higher than those following the placebo, not only for words they had worked on during the treatment, but for other words as well.

Dr. Fridriksson says that the stimulation technique could possibly be customized to address a patient’s needs, no matter where the lesion is located and no matter what type of aphasia he or she may have.

“Animal model studies show clearly that if you apply low-current stimulation to neural tissue it increases the amount of neurotransmitters that promote brain plasticity,” he said. “I don’t think there’s any reason why this brain stimulation should be specific to anomia. I think you could apply it to pretty much any therapy for aphasia.”

Dr. Fridriksson acknowledges that more clinical research is needed to understand how tDCS might be used to treat aphasia, and his plans are to apply for a grant to conduct a clinical trial on the technique. In the meantime, he’s also working to determine the ideal length of time to stimulate the patient during treatment. He is also using fMRI to determine how, specifically, tDCS activates the brain in people with aphasia.